Treadle switch



Jan. 3, 1950 c. N. MERRALLS ET AL I 2,493,157

TREADLE SWITCH Filed Dec. 10, 1947 5 /a /6 I I7 22 20 2/ Mmufiglnl mm M I LHI ' INVENTORS CHARLES N. MERRALLS Y HUBERT E. MELCH/OR WMKW ATlU/PNEVS Patented Jan. 3, 1950 "T" T "OFFICE TREADLE SWITCH Charles N. Merralls and Hubert E. Melchior, "Los Angeles, Calif.

Application December 10, 1947, Serial No. 790,778

Claims. 1

This invention relates generally to treadle switches, and more specifically contemplates unitary switch mechanism and actuatingmeans therefor adapted to control Y. electrical circuits in which the switch is interposed. incident to variation in lateral pressure applied thereto.

Treadle switches have heretofore 'foundtheir widest utility as devices for the control of electrical mechanism 'adapt'ed' to be energized by automotive vehicles. the switch is embedded in the street, driveway or roadbed so as to receive the weight of the vehicle passing 'thereover, and thus close'or open a circuit throughelectrical mechanism of any of various types, as for example apparatus for controlling trafilc signals, gates, garage doors, etc;

A common form of treadle switch having numerous advantages in installation and economy of manufacture comprises a pair of wire contacts encased in a'common dielectric and normally held by the 'latterin spaced, vertical alignment. The weightv by which the switch is to be actuated, imposed vertically thereon, is effective to displace the dielectric and force the contacts together to completean electrical circuit through the mechanism controlled thereby. However, as such devices, in the applications indicated, are ordinarily continuously exposed to the elements and are subjected to heavy pressure, their lifeis limited, and necessary repairs are frequent. .A'commonicauseof failureresults from the tendency of rubber or other dielectric casing for the contacts to crack or split, permitting the ingress of moisture and corrosive substances. Accordingly, short circuitingis commom, and early destruction of thecontactsthemselves :is an inevitable result.

'A principal object of the present-invention is to largely obviate the deficiencies of-the prior'art above referred to by the provision of a treadle switch operable in response to lateral pressure upon an elongated mechanical control medium to actuate a switch mechanism completely sealed by-means independent of the'outer sheathing of the .treadle.

More specifically, it is an object hereof to provide a treadlecomprising a resilient member sealed within a flexible casing 'and suspended thereby above afirmsupport-whereby pressure upon any intermediate reach of the encased member is eifective to relieve pressure of one end of the member-upon azsprlng-presse'dswitch contact, whereby-the spring jofthe switch mechanism is operable to actuate the latter.

In accordance therewith,

r v Another'object isto provide in a device of the character above alluded to, a casing for the switch-actuating element, comprising a flexible cable and a resilient-sheath adapted to perform the dual function of sealing the cable and actuating element and supporting the latter in an elevated position from which any reach thereof maybe depressed to effect the withdrawal from the switch of one end of the actuating element adapted normally to maintain the switch mechanism in predetermined condition. H

Another object is to provide a bridge-support for the actuating element, having laterally extending supporting flanges and an .intermediate void or air space disposed directlybelow a centrally located bead through which the actuating element extends, the bottom of the bridge support being substantially flat and sealed to prevent debris froin entering the void where it might limit the requisite distortion of the element or damage the lower wall of the bead in response to the'pressure thereon.

Still another object is the provision of a switch casing, adapted to be'permanently mounted in a'position laterally of the treadway, containing a switch having a'control member disposed across an opening in the side of the casing through which one end of the tread-actuated element projects, the flexible cable enclosing the actuating element being rigidly secured and sealed to the switch casing to obviate admission into the latter of moisture penetrating the outer sheathing.

Other objects and salient advantages of our invention, such for example as simplicity of construction, economy of manufacture, ease of installation, permanence and durability, as well as positive and permanent sealing of the switch contacts and terminals, susceptibility to standardization with respect to actuating Weight or pressure and compactness, will be apparent to those of skill in the artupon an examination of the following description read in the light of the accompanying drawings, in which:

Fig. l is a longitudinal vertical section, partially .in elevation, through a treadle switch embodying my invention;

Fig. 2 is a plan view, partially broken away, of the device shown in Fig. 1;

Fig. 3 is a broken side elevation, partially in section, depicting the effect of the weight of an automotive vehicle upon the actuatingassembly; and

Fig. 4 is a sectional view taken on line 4-4 of Fig. 1.

Referring to the drawings more in detail, the numerals of which indicate similar parts throughout the several views, 5 designates a flat casing, rectangular in plan, and divided by a partition 6, offset toward one end thereof. The larger compartment I of easing 5 forms a receptacle for electrical conductors 8 and 9 fed into the casing through a suitable conduit (not shown) for which a circular opening ii! is provided in the bottom of the receptacle. The wires 8 and 9 are connected to a pair of terminals I! mounted upon the transverse partition 65 through which wires an electrical circuit may be completed and broken by means of a switch 52 of conventional construction carried within the smaller section of the casing. The switch mechanism I2 is sealed permanently within the smaller section [3 by a coverplate [4. Similarly, the terminals ll of switch [2, extending into the larger section 1 of the casing, are sealed against moisture by a suitable insulating material with which the section I is filled after connection of the switch in the circuit at the point of its intended use.

Switch I2 is of the normally closed type and is held open by lateral pressure, applied by means hereinafter described, upon a resilient plate I 5 forming a part of the switch and attached permanently to one side of the switch body so as to extend adjacent and substantially parallel to the end iii of casing 5.

Projecting laterally from the center of, and forming a right angle with the end 16 of the casing, is a tube [1. The bore of tube ll opens to the interior of the switch housing 2, and loosely accommodates one end of a flexible wire or rod I8 adapted to normally bear against the resilient plate l5 of the switch so as to hold the latter open in response to its pressure thereagainst. The length of rod l8 varies in specific embodiments depending upon the ground area over which switch control is required. For example, where the device is to be actuated by a motor vehicle in conjunction with mechanism for opening and/or closing a garage door, gate and the like, rod i 8 is of a length to extend transversely across the driveway, roadbed or garage floor a distance sufficient to insure that one or both wheels at one side of the vehicle pass over the rod.

The rod is encased within a flexible cable i9, one end of which is fitted into and secured rigidly in the outer end of tube I! with its opposite end terminating slightly short of the opposite end of the rod. The outer end of cable is is sealed around the rod 18 by a weld or braze, as indicated at 20, which is effective to resist relative longitudinal movement between the cable and rod ends. The extreme outer end of rod i8 is beaded as at 2| to form an annular constriction between the end of cable l9 and the bead 2i for a purpose later referred to. The cable is not normally longitudinally compressible, and, being firmly attached to rod H3 at the outer end of the latter and to the tube 5 5 of the casing 5, normally holds the end of rod i8, projecting into the easing, firmly in contact with the resilient plate i5 of the switch, the pressure of the rod, when the rod and cable are straight, being sufiicient to maintain the switch open.

The entire cable 5 9, tube l1 and the beaded tip 2| of rod [8 are encased within a treadle-sheath 22, composed of rubber or other resilient material. Sheath 22 comprises an elongated flat bottomed base section having formed integrally therewith an upstanding bead 23 through which a hole 22 extends for projection of the cable I9. Hole 23 is spaced from the bottom of sheath 22 a distance substantially corresponding to the distance between tube I! and bottom of casing 5 so as to support the cable 19 and rod 18 in a horizontal plane when the casing 5 and sheath 22 are correspondingly positioned.

The laterally-projecting sides of the bottom of sheath 22 afford a means for clamping the latter within a suitable frame (not shown) with which conventional treadle switches are commonly equipped, so as to support the upper arc of the bead above the adjoining portions of the frame.

It will be observed that as tube ll is sealed to the body of casing 5, and cable I9 is similarly sealed to the end of tube I! and to outer end of rod iii, no moisture can enter the switch casing through the bores of the cable and tube. However, in order to avoid corrosion of the cable, the end of sheath 22 encasing the tube i1 is vulcanized to the end wall I6 of the casing and its opposite end completely encloses the beaded tip 2! of rod it as indicated in Fig. l. The restriction formed between bead 2| and the cable end is thus filled with the material of which the sheath is formed so as to insure an effective seal and to resiliently resist movement of the outer end of the rod i8 toward the switch casing upon flexing of an intermediate reach of the cable and rod in accordance with the operation of the device as is hereinafter more fully described.

The sheath 22 includes a flat air chamber 25 extending throughout its length below cable [9. The air chamber 25 is sealed at each end by a plug 26 vulcanized therein, so as to provide a void in the material into which cable l9 and rod It may be depressed upon the application of pressure to any intermediate reach of the treadle assembly. It will be appreciated that a portion 2! of sheath 22 immediately below cable I9 is quite thin to facilitate the depression of the latter while preserving the sealed condition of the cable. Similarly the lower wall 28 or bottom of air chamber 25 is imperforate to preclude the entry of any substances below cable l9 which might interfere with the effective flexing of the rod in response to pressure upon the treadle assembly. The completely sealed chamber 25 is of a width equal to or slightly greater than the width of bead 23, whereby an entire reach of the bead may be depressed incident to pressure upon the upper arc thereof, so as to minimize distortion of bead 23 incident to obtaining the required flexure of the rod.

The operation and utility of the device is further briefly described as follows: The unit is preferably installed in the roadbed, floor, driveway or the like with the switch casing 5 disposed at the edge of the treadway where it is protected against damage by the vehicles or other means by which the switch is to be actuated. The treadle sheath 22, with encased cable l9 and rod 18, suitably mounted within a frame adapted to maintain its position, is arranged to project across the treadway a sufficient distance to assure reception of the weight of the vehicle, the upper arc of bead 23 extending slightly above the plane of the treadway.

The weight of the vehicle moving across the treadle depresses the section of the sheath bead 23 and corresponding reach of the cable [9 and rod l8, encased thereby, into the chamber 25.

anemia Thehendhig .ot the;=treadle: to; causes contraction; of the end. of .the..;rod :I-il. projecting intothe switchcasing I3. Thismovementgoi; the rod. end is: efiected. as. a result of seizeral independent. .actionsoi. the. parts of the treadie, ,asaboutv vto be described, each of. which are. capable of causing the. required; movement oitherodfend, but. in the embodiment illustrated. all cooperate to actuate the switch i2. With 120d. l8 disposedjwithin. cable 1a,. flexing of; these elements; tends. to retract both ends .of boththe d. and cable, but, due to the difierencesr dini the curves imposed upon-these elementssthe ends of. the-rod tend to be retracted-to a reater extent. However, as the outer end of; the rod is firmly held by the. normally incompressible cable, this. greater retraction of theqrod is concentratedat the end thereof which extends into contact with the switch plate It.

Moreover, as above indicated, one end of cable I9 is rigidly attached to the .end of tube H, and the opposite end of. the cable is mounted firmly in the rubber sheathing; thus substantiallongitudinal movement of one of. the cable ends is firmly resisted while the other end is resiliently re sisted. Being flexible and slightly nextensibla, however, the cable largely absorbs and localizes the distortion resulting from the weight of the vehicle thereon. The. resilience of the material of which the sheathing 22 is formed, while reinforcing the position of: the outer end of the cable l9 as immediately above described, permits slight contraction of the outer end of the cabl uponv fiexure of an intermediate reach thereof. The rod i8, however, being secured at only its outer end, ispermitted by the cable 49 and sheath .22 insufficient longitudinal movement to absorb the lateral displacement of its intermediate reach inresponse to substantial pressure thereon. Accordingly, the opposite free end of rod l8 extending into the switch casing is retracted into the bore of tube ll, thus relieving pressure upon switch plate l5 and permitting the switch to close in response to the urge of resilient means forming a part of the switch mechanism.

Upon relaxation of the pressure on the treadle assembly, the resilience of the rod [8, cable I9 and sheath 22 compels the return of these elements to their original position, again projecting the free end of the rod against the switch plate l5 so as to re-open the circuit. The momentary closing of the switch I2 permits its utility for control of a circuit through a relay (not shown) by which the primary circuit through the electrical mechanism to be actuated is controlled.

It will thus be seen that we have provided a flexible treadle adapted to be distorted in response to pressure thereon so as to shift one end of an element of the treadle with respect to laterally-disposed switch mechanism with which it is normally engaged, for actuating the latter, the arrangement of the elements bein such as to assure complete protection of the metal components of the treadle from corrosion and of the switch mechanism per se from moisture.

While we have shown a preferred embodiment of the invention, it will be appreciated that the device specifically alluded to is merely illustrative of certain essential features which may be incorporated in many forms and arrangements within the skill of those in th art, and that the outer end of the rod may extend slidably through the corresponding end of the cable for attachment to a suitable mounting, that the outer end 6 otilthdcablie'zmazyjdie.mhnilarlytimountediandaaha. sorb; the lateral .spressuresagainst fits mtermeda. ate. portion; incident solely to its inherenttereesilience, that the cable may hex-movable throughthe. sheathin response t.o;.lat.eral' pressuretherew against independent; or the rod, andthat. where; occasion. requires. a. single: treadlesmay' be: (cine ployedtomechanically control the operation-13f. a.=pair :of switches located at opposite endsof;

. the -treadle.assembly,..all without-departing from the spiritroisour"intention as defined in the *ap; pendedelaims.

What we claim and desire to secure :byLettcrs; Patentris:

1. In a treadle switch mechanism, a pair or flexible members. .coaxially dis osed, means to" secure corresponding-ends -:of said members rigs idly together :to resist relative longitudinal move ment therebetween, a casing, and means to :se

cure the opposite end of the outer flexible. mem

ber tosaid casing,,-the:oppo'site end of .said'inner member extending into said casing and movable; longitudinally relative, to the latter in. response:

to flexing oi .anlintermediate reachzofzsaid inner? member.

2. In a treadle switch mechanism, a flexibletubular member and a flexible elongated member coaxially disposed and having :one pair of cor responding ends thereof connected, rigidly toe gether, the .oppositeends'of said members; bein movable, longitudinally. with respect to one an other; the outer member being composed ofv noncompress'ible material to. resist; retraction oi thfl."

end. of. said inner member connected thereto incident to joint flexin of said members whereby lateral. displacement .of an intermediate reach. of said. members is effective to retract the relatively movable end'of said inner member, and

means to hermetically seal. the endof said .outer' member that is connected to said inner member.

3. In a treadle switch mechanism, a casing having an opening in one end thereof but otherwise hermetically sealed, a switch in said casing, a. treadle member extending reciprocably into said casing and engaging said switch, and a flexible, non-contractible tube encasing said treadle member having one end sealed to said casing and the opposite end sealed to the corresponding outer end of said member.

4. In a treadle switch mechanism, a switch, a flexible treadle member having one end engageable with said switch to actuate the latter in response to longitudinal movement, and means includin a flexible sheath for said member engaged rigidly with the opposite outer end of said member to resist relative displacement of the latter outer corresponding ends of the member and sheath whereby flexing of said membe and sheath is operable to retract said switch-engaged end of said member.

5. In a treadle switch mechanism, a switch, a. treadle member havin one end engageable with said switch to actuate the latter in response to longitudinal movement of the member, a tube encasing said treadle member, and means to resist longitudinal movement of the ends of said tube, the switch-engaging end of said treadle member being slidable through the corresponding end of said tube, and the opposite end of said treadle member being secured to said tube.

6. In a treadle switch mechanism, a switch, a treadle member having one end engageable with said switch to actuate the latter in response to longitudinal movement of the member, a tube encasing said treadle member, means to secure the end of said tube encasing the switch-engaging end of said treadle member against movement relative to said switch, and means to resiliently resist longitudinal movement of the opposite end of said tube, said treadle member having its switch-engaging end slidable in said tube and its opposite end secured firmly to the corresponding end of said tube, and means to her metically seal the last-named end of said tube.

' 7. In a treadle switch mechanism, a casing, a switch sealed within said casing, a flexible tube connected to one side of, and opening into, said casing adjacent said switch, and a flexible treadle member within said tube having one end projecting into said casing to actuate said switch in response to longitudinal movement thereof, the outer end of said tube being sealed and secured to said treadle member to resist relative longitudinal movement between the outer end of said treadle member and said tube.

8. In a treadle switch mechanism, a switch, a casing for said switch having an opening therein, a flexible treadle member having one end extending into said casing through said opening to actuate said switch in response to longitudinal movement of said member, means to secure the opposite end of said member against substantial longitudinal movement relative to said switch whereby flexing of said member is efiective to retract said switch-actuating end of said member, and means to encase said member, and means to hermetically seal said last-named encasing means to said casing around said opening.

9. In aswitch mechanism, a switch casing, a switch in said casing, an elongated block of resilient and compressible material having one end hermetically sealed to one side of said casing, a flexible, non-contractible tube in said block and having one end secured rigidly to said side of the casing, an elongated, switch-actuating member extending loosely through said tube, having one end projecting into said casing to actuate said switch in response to longitudinal movement of said last named end of said member, and the other end of said member secured rigidly to the outer end of said tube, said casing and said block coacting in hermetically sealing said switch and said switch-actuating member.

10. In a switch mechanism, a switch casing, a switch in said casing, an elongated block of resilient and compressible material having one end hermetically sealed to one side of said casing, a flexible, non-contractible tube in said block and having one end secured rigidly to said side of the casing, an elongated, switch-actuating member extending loosely through said tube, having one end projecting into said casing to actuate said switch in response to longitudinal movement of said last named end of said member, and the other end of said member secured rigidly to the outer end of said tube, said casing and said block coacting in hermetically sealing said switch and said switch-actuating member, the outer ends of said tube and member being secured within and to said block to resiliently resist movement of said ends relative to the casing.

CHARLES N. MERRALLS. HUBERT E. MELCHIOR.

REFERENCE S CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,944,147 Forman Jan. 23, 1934 2,213,409 Quilliam Sept. 3, 1940 2,244,933 Armstrong June 10, 1941 

